Weaving innate lymphoid cells (ILC) into the fabric of asthma exacerbations

Interleukin-33 increases type 2 innate lymphoid cell count and their activation in eosinophilic asthma

BACKGROUND

Interleukin-33 (IL-33) exacerbates asthma probably through type 2 innate lymphoid cells (ILC2s). Nevertheless, the association between eosinophilic asthma (EA) and ILC2s remains obscure, and the mechanisms by which IL-33 affects ILC2s are yet to be clarified.

METHODS

ILC2s were evaluated in peripheral blood mononuclear cells, induced sputum, and bronchoalveolar lavage fluid obtained from patients with EA. Confocal microscopy was performed to locate ILC2s in lung tissue and the mRNA expression of ILC2-related genes was also evaluated in the EA model. The proliferation of ILC2s isolated from humans and mice was assessed following IL-33 or anti-IL-33 stimulation.

RESULTS

The counts, activation, and mRNA expression of relevant genes in ILC2s were higher in PBMCs and airways of patients with EA. In addition, ILC2 cell counts correlated with Asthma control test, blood eosinophil count, Fractional exhaled nitric oxide level, and predicted eosinophilic airway inflammation. IL-33 induced stronger proliferation of ILC2s and increased their density around blood vessels in the lungs of mice with EA. Moreover, IL-33 treatment increased the counts and activation of ILC2s and lung inflammatory scores, whereas anti-IL-33 antibody significantly reversed these effects in EA mice. Finally, IL-33 enhanced PI3K and AKT protein expression in ILC2s, whereas inhibition of the PI3K/AKT pathway decreased IL-5 and IL-13 production by ILC2s in EA.

CONCLUSIONS

ILC2s, especially activated ILC2s, might be critical markers of EA. IL-33 can induce and activate ILC2s in the lungs via the PI3K/AKT pathway in EA. Thus, using anti-IL-33 antibody could be a part of an effective treatment strategy for EA.

Asthma Management in Adults

Management of asthma in adults has advanced in the past 10 years. Central to these advances has been further clarification of type (T) 2 mechanisms of airway inflammation and utilization of T2 biomarkers, that is, eosinophils and fractional exhaled nitric oxide. In addition, epithelial cells are emerging as significant contributors to inflammation through generation of alarmins to initiate local injury as well as downstream pathways. Five new biologics, mepolizumab, benralizumab, reslizumab, dupilumab, and tezepelumab, were approved to join omalizumab and revolutionize severe asthma treatment. These biologics significantly prevent exacerbations to spare systemic corticosteroids use and their side effects. Guidelines attest to the effectiveness of inhaled corticosteroids/long-acting β-agonists (formoterol) for both maintenance and rescue therapy. Focused updates to the Expert Panel Report addressed limited but specific questions relevant to asthma control. Future guidelines should include phenotype/endotype-directed therapeutics to gain more precision-directed treatment.

Asthma exacerbations: the Achilles heel of asthma care

Asthma exacerbations significantly impact millions of patients worldwide to pose large disease burdens on affected patients, families, and health-care systems. Although numerous environmental factors cause asthma exacerbations, viral respiratory infections are the principal triggers. Advances in the pathophysiology of asthma have elucidated dysregulated protective immune responses and upregulated inflammation that create susceptibility and risks for exacerbation. Biologics for the treatment of severe asthma reduce rates of exacerbations and identify specific pathways of inflammation that contribute to altered pathophysiology, novel therapeutic targets, and informative biomarkers. Major steps to prevent exacerbations include the identification of molecular pathways whose blockage will prevent asthma attacks safely, predictably, and effectively.